Articles of composite structure having appearance of wood

ABSTRACT

A door or other entryway component of synthetic resin composite construction and closely resembling the appearance of stained real wood. Skin portions of doors and other structures have a surface layer of clear gel coat resin molded to include the texture of a wood grain surface. A subsurface layer adjacent the clear gel coat layer is of pigmented gel coat resin. A structural support layer of the skin is of reinforced resin. Skins of a door or similar article are mounted on frames, and dense micro porous resin foam is provided between the skins to form a solid structure such as a door. Moldings retaining glass panels in openings defined in the door or similar structure are attached to the skins by adhesively fastening the moldings to the skins. Fasteners mounted in the moldings so that there are no plugged holes in the exterior surfaces of the moldings are used to locate the moldings properly with respect to the skins by inserting the fasteners into predrilled holes in the skins. The assembled doors and other structures can be finished by staining and coating with a finish system such as a urethane varnish to provide an appearance closely resembling real wood.

BACKGROUND OF THE INVENTION

The present invention is related to articles of composite constructionincluding reinforced synthetic resins, and in particular relates to sucharticles finished to resemble the appearance of real wood.

Real wood, finished by staining and provision of a protective coatingsuch as natural or synthetic lacquer, varnish, or resin finishes, has apleasing appearance and a substantial and solid feel. Many species ofwood having a desirable appearance, however, such as most hardwoods, areexpensive and require considerable amounts of skilled labor and time forproduction of finished articles. The appearance of wood with a brightfinish, that is, a finish exposing the color and texture of the woodgrain, is particularly desirable for exterior doors and entrywaystructures, although they may be quite expensive to construct of realwood.

While the appearance of wood is very pleasing for entryways and otherexterior features of building, wood is susceptible to damage caused byweather and insect pests, which can destroy the wood or damage itsfinish. Frequent and often costly maintenance is thus required toprevent rapid deterioration of the appearance of real wood with a brightfinish exposed to the weather.

As a more economical substitute, then, entryway doors and numerous otherproducts for which the appearance of wood is desirable have recentlybeen made of composite construction including outer layers offiber-reinforced synthetic resins prepared to resemble wood. Theappearance of such previously available imitation wood products,however, has at best failed to match the attractiveness of well-madestructures of actual wood with a bright finish.

While some products of plastics and composite construction have beenmolded to include surface texture resembling the grain of wood, theappearance of depth that is so attractive in real wood has previouslynot been possible to reproduce in the finish of such articles. Forexample, Mrozinski U.S. Pat. No. 5,399,373 discloses production ofimitations of natural wood by molding a resin-based gel coat to includea surface shape closely copying the surface grain texture of real wood.For this layer Mrozinski teaches the use of a pigmented gel coatmaterial whose color is related to the color of the wood being imitated.Mrozinski's process also requires the use of artists' oil colors orsimilar pigments to fill the surface texture to imitate the appearanceof real wood. The use of such artists' oils, however, requiresconsiderable skill and time, and still results in an appearance somewhatlacking in realism.

Doors and other entryway components frequently include panels surroundedand supported by moldings attached to larger frame members. Such panels,particularly glass panels of doors and entryway sidelights, have to besupported securely with respect to the surrounding frames. The weight oflarge multi-layered glass panels, particularly when they includedecorative panes assembled in metal caming, can be significant. Moldingsused to attach such glass panels to frame structures must therefore beheld securely in the required locations on a door or other framestructures.

While adhesives are the primary mechanism for interconnecting the partsof synthetic resin composite structures, fasteners extending through themoldings have also been required in previously known doors and otherstructures of composite construction in order to ensure that heavy glasspanels are held securely enough. The holes through the moldings wheresuch fasteners have been installed have then had to be plugged andfinished to match the surrounding surfaces of the moldings, requiringsignificant time and skill.

What is desired, then, is an improved composite construction includingsynthetic resin surface portions that can be finished to provide anattractive pleasing appearance closely resembling finished natural wood,while avoiding the disadvantages of natural wood. It is also desired tobe able to secure moldings to the skins or other components of a door orother structure of composite construction without having to usefasteners that extend through the moldings to their exterior surfaces.

SUMMARY OF THE INVENTION

The present invention provides an answer to the above-stated need for aproduct of composite construction having an appearance closely imitatingreal wood, by providing a structure for the exterior skin of a productof composite materials incorporating synthetic plastics that whenfinished has the appearance of real wood, and by providing a method formaking such products.

As first aspect of the invention, an article manufactured of compositematerials and having an appearance closely resembling real wood includesan outer layer of a transparent resin-based gel coat material whoseouter surface is molded to incorporate in detail the grain shape of thesurface of bare real wood. A subsurface layer adjacent to the surfacelayer of transparent gel coat material is of pigmented resin-based gelcoat material of a color related to or resembling the color ofunfinished wood of the type whose surface shape is represented. Beneaththe subsurface layer is a structural supporting layer which may be of asuitable synthetic resin, reinforced as by glass or other fibers.

When an appropriate finish, such as a wood stain and a protectivecoating such as laquer, varnish, urethane, or another suitable syntheticresin, is applied to the outer surface of the outer layer of clear gelcoat material, the resulting appearance of such a structure according tothe invention has a remarkable resemblance to real wood with a similarstain and protective finish. An article constructed according to theinvention and provided with such a finish presents an appearance ofdepth closely resembling the appearance of real wood with a similar typeof finish.

In one preferred embodiment of this aspect of the invention the outerlayer of transparent gel coat is substantially completely clear andcolorless.

In one preferred embodiment of this aspect of the invention the outerlayer of transparent gel coat has an average thickness in the range ofabout 0.012 to 0.020 inch, while the subsurface layer of pigmented gelresin has an average thickness in the range of about 0.003-0.010 inch.

A second major aspect of the present invention is the method ofmanufacturing an article of composite structure by providing a firstskin sheet including an outer layer of transparent gel resin molded toincorporate a surface shape imitating the grain of real wood; providinga second skin sheet, fastening the skin sheets to opposite faces of aframe structure; filling the cavity defined between the skin sheets andwithin the frame structure with a structural synthetic resin foamadhering to the frame structure and the skin sheets; curing the resinfoam and thereby forming a substantially rigid core structureinterconnecting the skin sheets and frame; and applying a protectivefinish coating to the outer surface of the outer layer of at least thefirst skin sheet.

A third aspect of the present invention is the provision of an articleof composite construction resembling an article of real wood andincluding fasteners fixedly mounted in moldings and used to locate themoldings precisely with respect to an article of composite constructionwithout the use of fasteners extending entirely through such moldings sothat unsightly plugs and difficult finish work are not needed.

The foregoing and other objectives, features, and advantages of theinvention will be more readily understood upon consideration of thefollowing detailed description of the invention, taken in conjunctionwith the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an isometric view of a portion of a door of compositeconstruction according to the present invention.

FIG. 2 is a sectional elevational view of a portion of a mold used toform a skin for an article such as the door shown in FIG. 1.

FIG. 3 is a view similar to that of FIG. 2 showing an outer layer of atransparent resin-based gel coat applied to the mold as part of theprocess of manufacturing a door skin.

FIG. 4 is a view similar to FIG. 3 also showing the addition of asubsurface layer of a pigmented resin-based transparent outer gel coatmaterial onto the transparent outer layer.

FIG. 5 is a view similar to FIG. 4 also showing the addition of a layerof reinforced resin to the previously present layers.

FIG. 6 is a sectional view of a portion of a door according to thepresent invention, taken in the direction indicated by line 6—6 in FIG.1, at an intermediate stage in the manufacture of such a door.

FIG. 7 is a view similar to FIG. 6 showing the portion of a door at asubsequent stage of manufacture.

FIG. 8 is a sectional view of a door constructed according to theinvention.

FIG. 9 is a view similar to FIG. 8, showing a door according to theinvention and that has an opening extending through it for receiving aglazed panel.

FIG. 10 is a sectional detail view at an enlarged scale showing aportion of the door shown in FIG. 9, with moldings in place to securelymount a glazing panel within the opening.

FIG. 11 is a sectional detail view showing a portion of the door shownin FIG. 1 and showing the layers of one system of stain and protectivefinish coats.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings which form a part of the disclosureherein, shown in FIG. 1 is a corner portion of a door 12 of compositeconstruction according to the present invention. As shown along theright hand side of FIG. 1, the structure of the door 12 is cut away toreveal its interior construction in section view. A pair of door skinsheets 14 and 16 imitating real wood are located on opposite sides ofand are adhesively attached to a frame structure 17. The frame structure17 includes a bottom rail of which an interior structural portion 18 maybe of a multilayered laminated wood material. An outer surface piece 20is of solid real wood, preferably of the species imitated by the skinsheets 14 and 16. The frame structure 17 also includes a pair of uprightstiles, each preferably constructed similar to the bottom rail shown inFIG. 1, and a horizontal top rail, the stiles and rails forming arectangular peripheral shape.

The frame structure 17 has a pair of opposite substantially planaropposite faces 22, and the skin sheets 14 and 16 are each attached to arespective one of the faces 22 by a suitable adhesive capable ofpermanently attaching the skins 14 and 16 to a wooden surface. Forexample, a suitable adhesive for attaching skin sheets 14 and 16 of theconstruction described below is “Plastic Welder II,” available from ITWDevcon, of Danvers, Mass.

Between the skin sheets 14 and 16 and within the area surrounded by theframe structure 17 the entire space between the door skin sheets 14 and16 is filled to form a core 24. The material of the foam core 24 ispreferably a relatively dense microcellular urethane foam produced inplace from a two-part self-rising composition. The foam material of thecore 24 preferably adheres strongly to the interior surfaces of the skinsheets 14 and 16 and the stiles and rails of frame structure 17, andthus helps to bond the component structures of the door 12 to eachother.

The outer surface of the skin sheet 14 of the finished door 12 has theappearance of real wood finished “bright” with a substantiallytransparent finish. Wood grain structures closely resembling thecorresponding structures in real wood are clearly apparent, as at 26 and28. Portions 26 simulate relatively open pore portions of the surface ofa piece of a hardwood such as, for example, oak, while portions 28represent the harder portions of natural wood grain structure. The skinsheet 16 is of substantially similar appearance, and imitates anopposite side of a door of the same real wood species.

The structure of each of the skin sheets 14 and 16 is critical to theability of the present invention to provide a door 12 or otherstructures with an attractive appearance closely resembling actual woodwith a “bright” finish.

According to the present invention a door skin sheet 16, or a skin sheetfor another article with a bright finished wood appearance, ismanufactured by preparing a mold 30 to reproduce faithfully the detailsof the surface configuration of an actual wooden model structure. Inpreparing a door skin sheet 16, for example, an actual wooden door ismanufactured, but its surface is left bare, and its grain structure ismade clearly apparent and accentuated by carefully sanding and wirebrushing the wood surfaces. The surface of the wooden model is thentreated to prevent it from sticking to the material of which the mold isto be made, as by spraying the wood surfaces with an appropriate moldrelease compound. From the model a mold is made of material capable ofreproducing fine detail, such as a conventional silicone rubber moldmaterial using conventional mold preparation techniques. For example, anRTV silicone rubber compound available from Performance Silicones, Inc.,of Chino, Calif., under stock number PSI 651B is suitable. The moldfaithfully reproduces the minute surface irregularities of the woodgrain of the model. As shown in FIG. 2, a mold surface 32 of the mold 30thus includes irregularities such as the projections 34 corresponding toopen pores in the grain of the surfaces of the wood of the model, whilerelatively smooth portions 36 of the mold surface 32 correspond to theslightly protruding harder portions of the grain of the wood of themodel from which the mold 30 is made. Thus, the projections 34 in themold 30 are intended to produce grain pore portions such as those inshown at 26 in FIG. 1, and the smoother parts 36 of the mold 30 areintended to produce correspondingly smooth areas such as those shown at28 in FIG. 1.

It is of critical importance according to the present invention toproduce a surface shape of an article such as a skin sheet 14corresponding closely with the surface of the piece of wood to beimitated. The surface shape alone, however, is insufficient to obtainthe desired appearance in the final product, as will be explainedpresently.

Referring next to FIG. 3, a skin sheet 14 or 16 is prepared by buildingup a succession of layers of material in the mold 30. After applying asuitable mold release compound (not shown) to the mold surface, a first,or outer layer 40 is applied to the mold surface 32, to an averagethickness 42 of, preferably, about 0.018 inch, although a thickness assmall as about 0.012 inch or as great as 0.020 inch would also besatisfactory. The outer layer 40 is of a transparent, preferablycompletely clear and colorless, resin-based gel coat material, althougha slight coloration is acceptable, so long as the outer layer 40 remainsessentially transparent. A preferred material for the outer layer 40 isa clear UV-curing unpromoted, polyester-based gel coat materialavailable from NESTE Polyesters, Inc. of Ft. Smith, Ark., under thetrademark NESTE MAXGUARD and designated as SL00221B, version #6. Such agel coat material may be applied to the mold surfaces 32 to the requiredthickness in uncured form by conventional spray application, and is thencured, leaving a relatively smooth and regular inner surface 44 of theouter layer 40. The preferred material includes fillers and UV resistantcomponents, but is flexible enough to withstand removal of the skinsheet 14 or 16 from the mold 30 without cracking.

When the outer layer 40 has been cured according to the manufacturer'sinstructions, a subsurface layer 48 of pigmented gel coat material isapplied to it and cured as it remains in the mold 30, in a thin butcomplete coat having a thickness 50 preferably sufficient for thesubsurface layer 48 to be substantially opaque and to appear solidlycolored as viewed through the outer layer 40.

Preferably, the subsurface layer 48 is a polyester-based gel coatmaterial with a uniform pigmentation similar in color to the lightestcolor present in the species of wood intended to be imitated by the skinsheet being prepared. As an example, using NESTE MAXGUARD base color gelcoat material in a thickness 50 of at least about 0.003 and preferablyabout 0.005-0.010 inch provides the needed opacity and definite color tobe visible with an appearance of depth beneath the outer surface 44 ofthe outer layer 40. For an imitation of mahogany a soft salmon colorpigment such as that available as NESTE's Mahogany gel coat NG32626,version #4, provides a good result, while for imitating oak a pinkishtan color such as NESTE's Pink Rose gel coat RG31515, Version #3, issatisfactory.

The combination of the textured transparent outer layer 40 and thepigmented subsurface layer 48 result in the desired appearance of thefinished skin sheet 14 according to the invention once the outer layer40 has been stained and provided with a protective coating material, aswill be described subsequently.

Once the subsurface layer 48 has been cured, a structural support layer54 is applied to adhere to the subsurface layer 48 to provide structuralsupport for both the outer gel coat layer 40 and the subsurface gel coatlayer 48. The structural support layer 54 may be, for example, of aconventional resin with embedded glass fibers. For example, a 3-ouncematt of glass fiber strands such as a VETROTEX CERTAINTEED continuousfilament glass fiber matt impregnated with an AOC ultraviolet curingpolyester resin layer may be applied to adhere closely to the exposedinner surface of the subsurface layer 48. A preferred resin for thestructural support layer 54 is an ultraviolet cured polyester resinRX1270 available from Alpha Owens Company of Perris, Calif. In smallspaces and corners of small radius, a suitable polyester-based adhesiveputty such as “PolyBond B38,” available from A.T.C. Chemical, Inc., ofBuffalo. N.Y., is used to avoid air pockets between the subsurface gelcoat layer 48 and the glass-reinforced resin of the structural supportlayer 54. The fiber-reinforced structural support layer 54 is then curedto complete the skin sheet 16. Preferably, the cured structural supportlayer 54 has a thickness 56 of about 70 mils, to make the overallthickness 58 of the skin sheet 16 of the door 12 equal about {fraction(3/32)} inch, although other articles may require different thicknesses.

A pair of skin sheets 14 and 16 prepared as just described arepreferably kept in their respective molds 30, and an appropriateadhesive material such as the previously mentioned “Plastic Welder II”is applied to appropriate portions of the surface of each structuralsupport layer 54. The two molds 30 containing and supporting the skins14 and 16 are then placed in properly registered locations to adhere tothe frame structure 17, as shown in FIG. 6, with each mold 30 adequatelysupported and pressed toward the frame structure 17 by a rigid caul (notshown).

The skin sheets 14 and 16, together with the frame structure 17, definea cavity 60, into which an appropriate quantity of a self-foaming resinmixture is placed. The molds 30 are supported adequately to resist theforce generated while the foam material expands to form a foam core 24fully filling the cavity 60 and adhering to the exposed surfaces of thestructural frame 17 and the structural support layer 54 of each of theskin sheets 14 and 16. The foam is formed in place by pumping in theappropriate quantity of freshly mixed foam forming compound after theskin sheets 14 and 16 have been attached to the structural frame. Thepreferred core density of 28 lbs/ft³ when expanded to fill the spacewithin the shell of the door 12 is slightly less than that of real wood.The resin foam solidifies to form a substantially rigid microcellularfoam core 24, shown in FIGS. 1 and 7.

After the foam core 24 has solidified and no longer urges the skinsheets 14 and 16 outwardly apart from each other, the molds 30 may beremoved from the skin sheets 14 and 16. The skin sheets 14 and 16 canthen be trimmed to the proper finished dimension flush with the surfacepiece 20 of each of the stiles and rails of the structural frame 17. Asshown in FIG. 8, the resulting door 12 includes a pair of skin sheets 14and 16, the structural frame 17, and the foam core 24, all of which areadhesively unified into a rigid structure having the weight and afeeling of solidity similar to that of a real wooden door of comparablesize.

Referring to FIGS. 9 and 10, for a door 80 similar to the door 12, butin which it is desired to have a glass panel, the door is preparedgenerally according to the same method set forth with respect to thedoor 12, except that the skin sheets 82, 84 include lips or flanges 86,88 surrounding an area where a panel is to be placed and directedinwardly toward each other to exclude the foam from where the panel isto be placed. Once the molds have been removed from the door 80, and inconjunciton with trimming the door skin sheets and surface pieces of thestructural frame, a suitable opening 90 is cut through the door 80 toreceive the intended glass panel 92 or the like, and a set of fastenerreceiving holes 94 are drilled in predetermined locations adjacent tothe opening 90 defined in the door 80 and surrounded by the flanges 86and 88. Suitable locations of the fastener receiving holes 94 are shownin FIG. 10, for example.

A pair of moldings 100 are prepared using the same method used toprepare the skin sheets 14, 16, 82, and 84, so that the exteriorsurfaces of the moldings 100 also include the wood grain shape detailsin an outer layer 40 of transparent gel coat material beneath which is asubsurface layer 48 of pigmented gel coat material, and beneath which isa structural support layer 102. The structural support layer 102 may besubstantially thicker than the structural support layer 54 of a skinsheet, since the molding is likely to be subjected to substantiallygreater and more concentrated stresses, as a result of its function insupporting a heavy glass panel 92. The glass panel 92 has a substantialweight, since it is triple-glazed and includes not only inner and outersmooth panes 104 of full size, but metal caming 105 supporting multiplepieces of decorative glass, with a total thickness 106 which may be, forexample, 1 inch.

Each of the moldings 100 also is provided with a foam core 108, whichmay be machined to fit against the skin sheet 82 or 84 and the flange 86or 88, as shown in FIG. 10. In conjunction with shaping the foam core108, sockets are machined and self-locking fasteners 110 to be receivedin the fastener receiving holes 94 are mounted in predeterminedlocations in the moldings 100. The locations of the fasteners 110 arepreferably established in the moldings 100 with the moldings 100 held ina suitable jig, and the fasteners 110 are then set precisely in an epoxyor other suitable adhesive 111 so that each fastener 110 is rigidly andsecurely fastened to the structural support layer 102 of the molding100.

The self-locking fasteners are capable of being received in appropriateholes and thereafter securely resisting withdrawal. They do not requirerotation during insertion, so there is no need for a hole extendingthrough to the outside of the molding 100. A suitable self-lockingfastener is of a molded synthetic plastic resin and is available fromAveco, of Detroit, Mich., as its number AVI4036 fastener.

One molding 100 may be placed into the required position in registrationwith the opening and the flange 88 in the skin sheet 84 on one side ofthe door 80 after applying a quantity of an adhesive material to theskin sheet 84. When the molding 100 is pushed toward the skin sheet 84the self-locking fasteners 110 associated with that molding are alsopushed into the fastener receiving holes 94 in the skin sheet 84. Thefasteners thus securely establish the position of the molding 100 withrespect to the door 80, particularly during the time while the adhesivematerial cures. With one molding 100 in place in the door 80, the glasspanel 104 can be placed properly with respect to the first molding 100,after which the other skin sheet 82 is provided with an appropriatelayer of adhesive material and the second molding 100 is placed againstthe opposite side of the door 80 and pushed into place so that itsfasteners 110 enter the fastener receiving holes 94 in the skin sheet 82locking that molding 100 into the required position with respect to thedoor 80.

Referring to FIG. 11, once the skin sheets 14 and 16 and, to the extentnecessary, the surface pieces 20 of the frame structure 17 of the door12 or the corresponding portions of the door 80 have all been trimmed tothe required size, and moldings 100 have been installed, the entire door12 or 80 can be provided with a protective, preferably clear andtransparent, finish 118. This is accomplished by application of a stainsuch as a wood stain applied in a conventional manner to fill the grainpores 26 and, to a lesser extent, to cover and color the portions 28representing the hard part of the wood grain represented by each skinsheet or molding. As when staining a real wood surface, it may bepreferable to use a stain system installed in two coats, first applyinga filler coat 120 to fill the pore portions 26. For example,Sherwin-Williams grain filler in the appropriate color for the woodbeing imitated, available from the Sherwin-Williams Co. of Cleveland,Ohio, may be used. Thereafter, a second, thinner, layer 122 of stain isapplied in generally the same manner used in staining real wood of thesame type. For the stain coat 122, Sherwin-Williams oil-based stain isused in the appropriate color to match the grain filler 120. Once thestain has been applied in the usual fashion, a durable protective finishcoating such as laquer, varnish, or a synthetic resin finish is appliedin much the same manner as in finishing wood, to coat the stainprotectively with a hard, scratch-resistant, transparent surface coathaving the desired glossy, matte, or satin surface texture. For example,two coats 124 and 126 of an acrylic urethane sealer coating such asSherwin-Williams Acry Glo Base Clear are applied followed by two coats128 and 130 of a clear acrylic finish coat such as Sherwin-WilliamsAcrylic Top Coat.

The combination of the transparent outer layer 40, with its thickness42, and the pigmented subsurface layer 48, give an appearance of acertain depth, so that with stain on the textured outer surface of theouter layer 40 and the protective finish coatings over the layer 122 ofstain the resulting appearance closely resembles that of a real woodsurface that has been stained and coated with a similar laquer, varnish,or synthetic finish material.

The terms and expressions which have been employed in the foregoingspecification are used therein as terms of description and not oflimitation, and there is no intention, in the use of such terms andexpressions, of excluding equivalents of the features shown anddescribed or portions thereof, it being recognized that the scope of theinvention is defined and limited only by the claims which follow.

What is claimed is:
 1. A skin sheet for a product of composite plasticsresin structure imitating the appearance of wood, comprising: (a) anouter layer of transparent gel coat material having an outer surfacemolded to replicate the shape of a wood grain surface; (b) a subsurfacelayer of pigmented gel coat material adhered to and located adjacentsaid outer layer; and (c) a structural support layer of fiber-reinforcedsynthetic resin material adhering to and supporting said subsurfacelayer.
 2. The skin sheet of claim 1 wherein said subsurface layer isclearly visible through said outer layer.
 3. The skin sheet of claim 1wherein said outer layer has a thickness in the range from about 0.012inch to about 0.020 inch.
 4. The skin sheet of claim 1 wherein saidouter layer has a thickness of about 0.018 inch.
 5. An article ofcomposite construction imitating a wooden item, comprising: (a) astructural frame having a pair of opposite faces; (b) a skin ofreinforced resin composition adhered to one of said opposite faces ofsaid structural frame, said skin defining an opening therethrough forreceiving a panel; (c) a panel located within said opening and fillingsubstantially all of said opening; and (d) molding of reinforced resincomposition extending adjacent said skin and said panel and overlyingsaid skin and said panel and helping to hold said panel in placerelative to said skin, said molding being located precisely with respectto said skin by a self-locking fastener extending through a receivinghole located in a predetermined position in said skin.